There are over 7 billion people living on the earth right now. Tens of millions are born and die each year. Every single one of us leaves signs of our existence in the air, water, soil -- even space.

Looked at another way, if one were to measure our planet's age as a single 24-hour day, the first human civilizations would appear less than a second before midnight. The geological time scale ...

The first human migrations out of Africa are thought ... are considered part of the same vast civilization, the Indus Valley Civilization, which thrived from 2600 to 1900 BCE.

Of all the known history in the area, however, one question remains – when did the first humans call the area ... the mound builders were a civilization that existed during the “woodland ...